1. Field of the Invention
The invention relates to a method and apparatus for producing crimped or curled fibre pieces of reconstituted tobacco of the type set forth.
2. Description of the Prior Art
Since the beginning of the fifties, in the tobacco industry both the tobacco dust occurring in the production and tobacco waste have been reprocessed and for example made into tobacco sheets which are then cut and supplied to the tobacco preparation in parallel with the tobacco. An overview of the various physical/chemical and processing possibilities is given in the article "Use of Reconstituted Tobacco has Soared", published in "Tabak Journal International", No. 2, 1981, page 84 et seq.
For the chemical engineering of the reprocessing of tobacco various possibilities have been developed; for example the published European Patent Application No. 0039647 proceeds from an apparatus in which the reprocessed tobacco composition is compressed by the screw of an extruder in a tapering outlet region and then pressed through a die plate before which a cutting blade is disposed. A disadvantage is the relatively high cleaning expenditure because for thorough cleaning of this extruder the entire apparatus must be dismantled. In addition, only rectilinear fibre pieces are produced which must be added to the tobacco preparation to give them the desired form corresponding to the tobacco fibres.
A particular constructional expenditure is required for one variant described in which the entire extruder is led past the rotating blade in a reciprocating pivotal movement.
A method and apparatus of the type set forth is disclosed in German Patent Specification No. 1,432,567, in which the thread-like intermediate products must be subjected to a subsequent very complicated post-processing to obtain the desired crimped fibre pieces. For this purpose the filamental intermediate products, which have a circular cross-section, must be rolled to intermediate products with flat cross-section and then dried in an air drier, this finally giving the crimped fibre pieces.